Oven temperature control with senser biasing winding



April 11, 1967 A. K. OTTO 3,313,484

OVEN TEMPERATURE CONTROL WITH SENSER BIASING WINDING Original Filed Sept. 26, 1963 J 1 1::|/j INVENTOR,

#rroF/VZOG United States Patent O OVEN TEMPERATURE CONTROL WITH SENSER Y BIASING WINDING Anthony K. Otto, Ann Arbor, Mich., assigner to King- Seeley Themas Co., Ann Arbor, Mich., a corporation of Michigan Original application Sept. 26, 1963, Ser. No. 311,739, now Patent No. 3,265,302, dated Aug. 9, 1966. Divided and this application Jan. 7, 1966, Ser. No. 519,350

15 Claims. (Cl. 236-68) This application is a division of Ser. No. 311,739 filed Sept. 26, 1963, now Patent No. 3,265,302. This invention relates to temperature sensing and control systems for use in a cooking oven, or the like, and more particularly to a temperature senser control therefor.

In cooking of meats or the like having substantial bulk and requiring a iinite amount of time to be brought to a desired cooking temperature, it is desirable to `operate the oven heat source at a higher `temperature setting at the beginning of the cooking operation to provide for fast heating of the roast to the desired cooking temperature. When the roast has reached `or as the roast approaches the desired cooking temperature, the temperature setting of the oven heat source must be lowered to maintain both the oven and roast at the exact cooking temperature preferred.

The principles of the invention are illustratively embodied in a senser unit comprising a length of wire having a high temperature coefficient of resistance and supported conveniently in the oven cavity in a location whereat the wire is subjected to temperature conditions of the oven. Changes in oven temperature cause changes in the resistance of the wire which are utilized to control the oven heat source which may be an electrical heating element or a gas llame, or the like. The control system is arranged to anticipate needs for heat changes in the oven and to change the condition of the heat source as necessary to maintain the oven `at a preselected temperature from the heat source with-out wide uctuations `above or below the preselected temperature.

The primary object of the present invention is to provide a new and improved temperature control system in which a temperature sensing device is subjected to the temperature condition of an oven or the like, and also is subjected to heat from an additional separate heating means.

Another object of the present invention is to provide a temlperaturre sensing pellet having a senser and a heater for the senser.

A further object of the present invention is to provide new and improved means of mounting a temperature sensing unit.

' Still another object of the present invention is to provide a new and improved temperature sensing pellet A further object of the present invention is to combine a temperature sensing wire having a high temperature coetiicient of resistance with a heating winding to control the response of the wire to temperatures applied thereto from a surrounding environment such as an oven.

Other objects and advantages of the present invention will be readily -understood by lthose skilled in the art to which this invention relates by reference to the following detailed description and the accompanying drawing, where- FIGURE 1 is a side elevational view, in section, of a control embodying the inventive principles;

FIGURE 2 is another side elevational view, partly in section, of the control shown in FIGURE 1;

FIGURE 3 is a bottom view of the apparatus shown in FIGURE 2; and

FIGURE 4 is a circuit diagram of a control system embodying the inventive principles.

Referring now to the drawing, in gener-al, the control unit comprises a temperature sensing pellet 10 mounted on a support bracket 12 by an insulating block 14. The control unit is adapted to be mounted, for example, at an appropriate position in or adjacent to an oven Icavity in a conventional manner.

The temperature sensing pellet 10` comprises upper plate means 16 having a centrally depressed portion 18 and a channel-shaped rim portion 20 including a reversely bent ange portion 22. The pellet 10` may be in the form of a disc and is further defined by lower plate means 24 in the form of an annular ring. Outer peripheral edge 26 is abuttingly received against the rim portion 20 and the inner edge 28 denes a central opening 29.

A senser unit 30 is sandwiched between the upper plate 16 and the lower plate 24 and comprises a pair of annular rings or plates 32, 34 which have inner abutting and xedly connected flange portions 36, 38 and spaced outer flange portions 40 and 42 which define an annular groove 44. The junction of the spaced plate portions 40, 42 provides a shoulder or hub portion 46. Inner rim portion 48 has a diameter substantially larger than the diameter of the opening 29 and terminates radially outwardly beyond the inner edge 28 of the lower plate. Spaced flange portions 40, 42 are supported in abutting engagement between the upper and lower plate means 16, 24. The senser unit 30 further comprises a plurality of turns of insulated wire 5t) having a high temperature 'coemcient of resistance and preferably wound on the shoulder 46 in abutting engagement with one another in a single layer between flanges 40, 42. For purposes of illustration, -the rst three turns of wire shown in FIG. 1 may be assumed to be turns of the temperature sensing wire although it is to be understood that any number of turns may be provided as required.

In addition, one or more turns of a heating winding 52 are wound in abutting engagement with an adjacent turn, illustratively shown to be the outer turn, of the sensing wire between the plate flan ges 4t), 42. Ends 56, 58 of the temperature sensing wire 50 extend radially inwar-dly between the abutting flanges 36, 38 and between the upper vplate 16 and the lower plate 24 for connection to. suitable electrical terminals. Similarly, the ends 6G, 62 of the heating wire S2 extend radially inwardly' betweenthe anges 36, 38 as shown.

T he pellet is supported on the insulating block 14 by a rim portion 64 and a central hub portion 66. Lower plate 24 is abuttingly received on the -rim portion 64 and the centrally depressed portion 18 of the upper plate is adapted to seat on the hub 66. A fastening element 68 extends through the upper plate, support block 14, and the bracket 12. As may be seen in FIG. 1, an annular cavity 70 is formed between the rim portion 64 and the hub portion V66. The ends of the wires 56, 58 and 60, 62 are adapted to be received in the annular cavity 70, and connected to a plurality of suitable termin-al plates 72, 74, 76, 78. The terminals 72, 74 are mounted on the ends of the shank 8i) of the fastener 68 in insulated relationship by a plurality of insulating washers S2, 84. Terminal 72 is electrically connected to the shank Vand terminal 74 is insulated therefrom by an insulating bushing 86. Wire end 62 may be connected to terminal 72 through the upper plate means and the fastener 68 while wire end 60 is suitably extended through the block 14 and connected to terminal 74. The end of the shank 80 may be peened over as indicated at 88 to xedly secure the contacts in sandwiched relationship against the bottom 90 of the bracket which provides a well 92 for the block 14. Terminals 76, 78 are fixedly mounted in the insulating block 14 and the upper ends 94, 96 protrude upwardly into the -central annular cavity 70 for connection to the Alead wires 56, 58.

The control circuit is shown diagrammatically in FIG.

4 and comprises a source of potential 110, senser unit 10, a conventional control device 111,- such as a bimetal 112 having a movable leg 113 controlling a pair of contacts 114, 116 to intermittently energize a heating element 11S to maintain `a predetermined oven temperature. FIG. 4 of the drawings symbolically represents heater 118 as a resistor. It is contemplated that in accordance with prior practices, element 118 represent the combination of a heater coil for an oven together with the relay which is customarily used to handle the power required by the heater coil such as in, for example, Hanssen Patent 3,069,- 524 granted December 18, 1962, and Boddy Patent 2,910,- 569 granted October 27, 1959, with or without a phase reversal, depending upon selected characteristics of devices 50 and 111, as is discussed in the latter patent. A heating winding 119 may be wound on the leg 113 in a conventional manner. The senser winding S and the heating winding 52 are located adjacent one another so that the temperature applied to the senser winding 50 is determined by the condition of the environment being sensed and by the energy state of the winding 52. A -senser 120, embodied in a meat probe or the like and adapted t-o be inserted into an article being heated by the element 118 in the oven to reflect the internal temperature of that article, is controllably connected to the heating winding 52. In this manner, energization of the heating winding 52 is controlled by the senser 120 so that the heat applied by heating winding 52 to the senser 5t) is proportional to the actual temperature condition of the roast, or the li-ke.

Consequently, when a roast is first placed in the oven with the internal temperature of the roast substantially below the'temperature at which the oven is set, the senser ll'causes the winding 52 to have a low energystate, for example, by utilization of a senser 120 having a high negative coeiiicient of resistance. Accordingly, the senser winding 50 is subjected primarily only to the heat in the oven derived from the heating element 118 and maintains the heating element 118 energized at la high rate to bring the oven to a preselected high temperature which may initially actually .be above the desired cooking temperature. As the temperature of the meat approaches the desired temperature, the energy state of the Vsenser 120 changes to permit more current to flow to the winding 52 and to subject the senser winding 50 to additional heat which changes its resistance. When, for example, the temperature of winding 52 is increased,l the temperature output of the element V118 will be reduced. This change in condition continues until the temperature of the article being cooked or heated, 4reaches or approaches an equilibrium temperature with its surrounding environment in the oven. Thereafter, the oven is maintained iat the desired cooking temperature during the cooking operation.

The inventive .principles hereinbefore described, may be alternatively embodied. For example, the senser may have a high negative temperature coeiiicient of resistlance and the senser 120 may have Ia high positive temperature coethcient of resistance. The particular control circuit with which the sensers are utilized may be varied as desired, and of course, various types of heating apparatus can be utilized in place of the electrical resistance element 118. Therefore, it is intended that the scope of the appended claims be construed to include various alternative embodiments and changes in the details of the contro-l system which utilize the inventive principles disclosed.

What is claimed is:

1. In apparatus for controlling the temperature of a mass being heated by `a source of heat in an environment including an environmental temperature controller and a heating element controlled. thereby, the combination of a support member, a temperature sensing unit including Vtemperature sensing resistance means supported in heat transfer relation with said environment, the environmental temperature controller including said temperature sensing resistance means for controlling the source of heat 1n respense to the temperature of the environment, a second sensing unit for sensing the temperature of the mass, and a separate heating resistance means thermally associ-ated with said temperature sensing means for changing the temperature condition of said sensing means in response to the sensed temperature of the mass and independently of heat supplied from the heating element except as 1t varies the tempearture of the mass, said temperature sensing means and said separate heating means being spirally wound in a coil in intimate heat transfer relation, one with the other, and plate means for `securing said sensing unit to said support member.

2. The temperature sensing device of claim 1 further including heat transfer plate means supporting plate means, portions of said supporting plate means being xedly connected in labutting engagement and other portions of said supporting plate means being in spaced `relationship and defining a resistance means cavity, said sensing resistance means being mounted in said resistance means cavity, and means xedly securing said supporting plate means to said heat transfer plate means.

3. The invention as defined in claim 2 wherein said heater means supplies control heat to said sensing resistance means.

4. The invention as defined in elaim 3 andjwherein said sensing resistance means comprises a spirally wound resistance means located in said resistance means ycavity in abutting engagement `with said supporting plate means, and said heater means comprises a spirally wound resistance element located in abutting engagement in said resistance means cavity with said sensing resistance means.

5. The temperature sensing device of claim 1 further including an insulated support member having a -central annular groove defined by a central hub portion and a spaced rim portion, a sensing resistance means housing comprising spaced. plate means, ysaid sensing resistance means being mounted between said plate means, one of said plate means 'being lconnected to said support 'member at said central hub position, the other of said plate means being connected to said support member along said rim portion, said plate means and said annular groove defining a terminal cavity, and portions of said sensing resistance means extending into said terminal cavity for electrical connection therein.

' 6. The temperature sensing yunit of claim 1 wherein said plate means includes la pair of plates, the outer portions of said plates being spaced from one another to define .an annular groove, the inner portions of s-aid plates being abutted to form a hub, said senser mounted in said annular groove in 4abutting engagement with said plates, and connecting end portions of said senser extending inwardly between said plates through the hub.

7. The temperature sensing device of claim 6 wherein said pair of plates includes an upper plate having a central depressed portion and a lower plate mounted in spaced relationship below said upper plate and forming a senser cavity therewith, said senser Xunit being mounted in said senser cavity, portions of said senser unit being abuttingly engaged with said upper plate in heat transfer relationship therewith, land connecting resistance means portions extending inwardly between said upper plate and said lower plate from said senser unit toward said central depressed portion.

8. The invention as defined in claim 6 and wherein said senser comprises said sensing resistance means spirally wound in abutting engagement with the hub.

9. The invention as defined in claim `6 and including said heating Winding means mounted on said plates.

10. The invention yas defined in claim 6 and including said heater resistance means spirally wound 'between said plates in heat transfer relationship with the senser.

11. The invention as delined in claim 1 and said sensing means and said separate heating means being mounted in a common housing.

12. The invention as defined in claim 1 and wherein said sensing means comprises a high temperature coeicient of resistance means, and said separate heating means comprises a heating resistance means wound in abutting engagement with said high temperature coeicient of resistance means.

13. The invention as defined in claim 12 and said high tempenature coeficient resistance meansl and said heating resistance means being sandwiched between parallel plate means.

14. The invention as defined in claim 13 and wherein said high temperature coefficient of resistance means and said heating resistance means are wound in ,a spiral in a single layer |between said parallel plate means.

15. The invention as defined in claim 14 and wherein said high temperature coefficient of resistance means and said heatingY resistance means are wound on -a `common abutment between said plate means, and the adjacent turns of each resistance ymeansy being in abutting relationship.

References Cited by the Examiner UNITED STATES PATENTS ALDEN D. STEWART, Primary Examiner. LOUIS R. PRINCE, Examiner. S. H. BAZERMAN, Assistant' Examiner. 

1. IN APPARATUS FOR CONTROLLING THE TEMPERATURE OF A MASS BEING HEATED BY A SOURCE OF HEAT IN AN ENVIRONMENT INCLUDING AN ENVIRONMENTAL TEMPERATURE CONTROLLER AND A HEATING ELEMENT CONTROLLED THEREBY, THE COMBINATION OF A SUPPORT MEMBER, A TEMPERATURE SENSING UNIT INCLUDING TEMPERATURE SENSING RESISTANCE MEANS SUPPORTED IN HEAT TRANSFER RELATION WITH SAID ENVIRONMENT, THE ENVIRONMENTAL TEMPERATURE CONTROLLER INCLUDING SAID TEMPERATURE SENSING RESISTANCE MEANS FOR CONTROLLING THE SOURCE OF HEAT IN RESPONSE TO THE TEMPERATURE OF THE ENVIRONMENT, A SECOND SENSING UNIT FOR SENSING THE TEMPERATURE OF THE MASS, AND A SEPARATE HEATING RESISTANCE MEANS THERMALLY ASSOCIATED WITH SAID TEMPERATURE SENSING MEANS FOR CHANGING THE TEMPERATURE CONDITION OF SAID SENSING MEANS IN RESPONSE TO THE SENSED TEMPERATURE OF THE MASS AND INDEPENDENTLY OF HEAT SUPPLIED FROM THE HEATING ELEMENT EXCEPT AS IT VARIES THE TEMPERATURE OF THE MASS, SAID TEMPERATURE SENSING MEANS AND SAID SEPARATE HEATING MEANS BEING SPIRALLY WOUND IN A COIL IN INTIMATE HEAT TRANSFER RELATION, ONE WITH THE OTHER, AND PLATE MEANS FOR SECURING SAID SENSING UNIT TO SAID SUPPORT MEMBER. 